Electrocardiography evaluation of heart work (ECG).

Plan of Lecture: 1. Formation of an electrogram of the heart muscle fibers (electrocardiogram) 2. Formation of an electrocardiogram during sending of excitation through the heart 3. Electrocardiographic leads: a) standard; b) enhanced; c) pectoral; 4. Characteristic of normal electrocardiogram 5. Analysis of electrocardiogram: a) determination of the excitation source; b) evaluation of heart rate; c) determination of heartbeating frequency; d) evaluation of electrocardiogram voltage; e) determination of the direction of the electrical axis; f) analysis of ECG-elements

Electrocardiogram It is the method of registration of heart bioelectrical potential from the chest of patient It is the method of registration of heart bioelectrical potential from the chest of patient

To describe how elektrocardiograma in all areas of wave of de- and repolarization sending will look you must remember three rules If the dipole vector directed towards the positive electrode of lead – ECG will show positive wave If the dipole vector directed toward the negative electrode lead – elektrocardiogram will show negative wave If the dipole vector is perpendicular to the axis of abduction, then elektrocardiogram writes isoline. Positive lead- electrode Isoline Vector of dipole Vector of dipole

ECG time & voltage ECG machines can run at 50 or 25 mm/sec Major grid lines are 5 mm apart, at standard 25 mm/s, 5 mm corresponds to 20 seconds Minor lines are 1 mm apart, at standard 25 mm/s, 1 mm corresponds to.04 seconds Voltage is measured on vertical axis Standard calibration is 0.1 mV per mm of deflection

Electrogram of cardiac muscle

ECG ELEMENTS WAVES OF ECG 1. P wave – depolarization of atria, precedes atria systole 2. QRS wave is depolarization of ventricles, precedes ventricular systole 3. atria repolarization also occurs at QRS 4. T wave indicates ventricular repolarization

ECG LEADS

a)Bipolar limb leads. The bipolar limb leads record the voltage between electrodes placed on the wrists and legs. These leads were proposed by Einthoven in 1913 I lead: left arm (+) - right arm (-); II lead: left leg (+) - right arm (-); III lead: left arm (+) - left leg (-) For recording limb leads we put red electrode on right arm, yellow - on left arm, green - on left leg and black - on right leg. Black electrode has zero potential (ground).

ECG LEADS

ECG LIMB LEADS

ECG AUGMENTED LIMB LEADS

ECG LEADS

The unipolar limb leads were proposed by Goldberger in They record voltage between single “exploratory electrode” from one limb and zero joined electrode from two other limbs. So there are three leads AVR, AVL, AVF. In fact zero electrodes records middle voltage of two limbs. Bipolar limb leads and unipolar limb leads record electrical power in frontal projection.

ECG LEADS

V1 - in crossing right IV right intercostal space and parasternal line; V2 - in crossing left IV intercostal space and parasternal line; V3 - between V2 and V4; V4 - in crossing V left intercostal space and medioclavicular line; V5 - in crossing V left intercostal space and anterior axilar line; V6 - in crossing V left intercostal space and middle axilar line.

ELECTROCARDIOGRAM

ECG leads

ECG LEADS

HOLTER MONITOR

SEQUENCE AND PROCEDURE OF ECG ANALYSIS 1.Determination of the excitation source. To determine the excitation source (pacemaker) it is necessary to assess the progress of excitation within atrium and set the correlation between P-wave and ventricular complexes QRS. Normally, the electrical impulse arises in the sinus node and ECG standard lead II record positive P-wave before every complex QRS. 2.Evaluation of correctness of heart rate – based on duration comparing of R-R-intervals. Normally observed an insignificant difference of duration within 0,1 sec 3.Determination of heart rate. With normal heart rate you should divide 60 seconds by the duration of R-R-interval in seconds 4.Evaluation voltage ECG. It is necessary to evaluate the amplitude of R- wave in the standard leads. If the amplitude of the R-wave in standard lead II more than 5 mm, or if the amount of R-wave amplitudes in the I, II and III standard leads is more than 15 mm, the voltage of ECG is maintained. 5.Determination of the electrical axis direction 6.Analysis of ECG elements

SIX-AXIS SYSTEM OF BAILEY Graphical method Calculate the algebraic sum of prongs amplitudes of the QRS-complex in I and III standard leads. Add it to randomly selected values ​​ on the axes of appropriate leads of 6-axis Bailey system of coordinate. From ends of these projections topostpone the perpendiculars. The point of their crossing connect with the the center of system. This line – is electric axis of the heart. The angle α is determined between this line and positive part of the axes I of the standard lead.

POSITIONS OF HEART ELECTRICAL AXIS IN NORM Vertical Intermediate horisontal

ANALISIS OF ECG ELEMENTS Analysis of P-wave includes: a ) evaluation of wave forms b ) measuring the amplitude and c) determine the duration. Analysis of segment interval and P -Q segment is measured from the end of P before Q. The interval is measured from the beginning of P to the Q. Analysis of the QRS complex includes: 1. Assessment of wave Q: a) measurement of its amplitude and compare it with the R wave amplitude in the same lead; b) measuring the length of wave Q 2. Assessment of wave R: a) measuring the amplitude and b) comparing it with Q wave amplitude in the same tooth extraction and other R leads. 3. Assessment of wave S: a) measuring the amplitude and b) comparing the amplitude of R wave in the same leads. Analysis of S-T segment. Analyzing segment, you must set its deviation from the isoline. Analysis of wave T. In the analysis of the T wave should: a) identify the direction, b) to assess its shape and c) to measure the amplitude. Analysis of the QT interval is to measure its duration (from the beginning to the end of QT).

FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE P -WAVE, INTERVAL AND SEGMENT PQ. Prong R in leads I, II, aVF, V2-V6 it is always positive in a healthy person. In leads III, aVL, V1 – can be positive, biphasic. In lead aVR – always negative. The amplitude of the P wave – to 2,5 mm, and its duration does not exceed 0,1 s. Interval P -Q reflects a time of spread of excitation within atrium, atrioventricular node, Gis bundle and its branches. The duration of the interval P -Q varies from 0,12 to 0,20 s, depending on heart rate. Segment P -Q reflects a spread of excitation throuh the atrio -ventricular node, Gis bundle and its branches. Duration of segment P-Q is normal to 0,12 sec.

FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE Q, R, S-WAVES Ventricular complexes ORST If the amplitude of prongs of ORS-complex more than 5 mm, they are given uppercase alphabet (Q, R, S), if less than 5 mm - capital letters (q, r, s). Duration of ventricular complex is 0,06-0,09 s in the standard leads Wave Q displays spread of excitation through the middle and lower thirds of the interventricular septum. It should not exceed 1/4 of prongs ʼ R amplitude in a healthy person, and its duration – 0,03 sec. But aVR-lead – is exception, where deep and wide Q-prong registered. Wave R normally registered in all standard and reinforced leads. In lead aVR R- prong slightly expressed or absent completely. In the precordial leads R-waves ʼ amplitude gradually increases from V1 - V4, and decreases in V5 - V6. Height of R wave does not exceed 20 mm in standard and reinforced leads, and 25 mm – in thoracic (pectoral). It displays the spread of excitation through the side walls of the right and left ventricles. Wave S Its amplitude in different leads varies in a wide range In a healthy person, but not exceeding 20 mm. Its duration – 0,03 s. Wave S decreases from V1, to V6 in the precordial leads. It displays the spread of excitation in the basal parts of the ventricles.

FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE T-WAVE, ST-SEGMENT AND QT-INTERVAL S-T segment – reflects full coverage of both ventricles with stimulation. As usual segment S-T is on the isoline in standard and reinforced single-pole leads from limbs and its displacement is less than 0,5 mm. In thoracalis leads lV1 - V3 may be a slight shift acording to the isoline up to 2 mm, and in V4, 5,6 - shift down less than 0,5 mm. Wave T – normally always positive in leads I, II, aVF, V2 - V6, moreover T1 > TIII and TV6 > TV1. It has aslope ascending and slightly steeper downward knee. In leads III, aVL and V1 – T wave may be positive, negative, or biphasic. In lead aVR negative T wave usually registers. The amplitude of the T wave is less than 5,6 mm in leads from limbs and mm in precordial leads. The duration of the T wave – 0,16-0,24 s. Q- T interval. This is an electrical ventricular systole. Duration of Q- T interval depends on heart rate. The proper duration time of interval Q- T can be counted with the Bazett formula: Q- T = K · √ R-R, where K - coefficient of 0,37 for men and 0,40 for women; RR - duration of one cardiac cycle or intercyclic іnterval.

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